Statistical evaluation and simplified approach for estimating excavation induced deformations in soft soils

This thesis is about estimating the deformation behavior of supported diaphragm walls and settlements behind the wall due to excavation built on soft ground environments. For this purpose, a finite element model that considers the stiffness of soils at small strain levels was utilized. With this model, numerous generic cases were analyzed. The accuracy of these generic cases and the parameters used were confirmed by a large number of cases, considering the parameters related to soil, wall, and excavation geometry as well as their variations. In this study, based on studies in the literature, the important parameters are selected to be the i) soil strength, stiffness, unit weight, and thickness of the soft soil layer, ii) the depth and width of the excavation, and iii) the stiffness of the support system. Unlike literature studies, the parameters representing the stiffness of the soil at the small strain level were calculated using empirical approaches. In statistical studies, using the multiple regression analyses, a closed-form solution that estimates the ground settlements and wall deflections based on mentioned parameters were proposed as a result of this study. In order to investigate the error level of the model, in addition to the error amount of the obtained regression equation, residuals were determined for the parameters and their ranges, moreover, the importance of each parameter on deformations was investigated. It is seen that the most important parameter affecting the behavior of this supporting system is the depth of the excavation. The results obtained from statistical approaches were compared with the real cases. It is seen that the proposed equations can predict the wall deformations and settlements in an acceptable range.